Photography – Fluid-treating apparatus – Fluid application to one side only of photographic medium
Reexamination Certificate
2003-02-07
2004-10-05
Rutledge, D. (Department: 2851)
Photography
Fluid-treating apparatus
Fluid application to one side only of photographic medium
C396S606000, C399S237000, C399S239000
Reexamination Certificate
active
06799908
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 2002-7026, filed Feb. 7, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to a developer unit for a wet-type color image forming apparatus, having a metering roller and using a high-concentration liquid developing agent.
2. Description of the Related Art
An image forming apparatus, such as a printer, photocopier, or scanner, includes an electrostatic latent image formation unit, a developer unit to develop the electrostatic latent image, and a transfer unit to transfer the developed image to a printing paper.
A conventional wet-type color image forming apparatus having the above structure is shown in FIG.
1
. In
FIG. 1
, reference numerals
100
,
102
,
104
, and
106
denote first through fourth photoreceptors in which electrostatic latent images to be developed into color images of cyan (C), magenta (M), yellow (Y), and black (K) are formed, respectively. Reference numerals
110
,
112
,
114
, and
116
denote first through fourth cleaning blades that respectively clean the first through fourth photoreceptors
100
,
102
,
104
, and
106
. Reference numeral
130
denotes a transfer belt to which the developed images are sequentially transferred from the first through fourth photoreceptors
100
,
102
,
104
, and
106
, thereby forming an overlapped color image to be transferred to a paper
90
. A plurality of rollers
132
,
134
,
138
,
140
,
142
, and
144
, which have different functions, are arranged inside the transfer belt
130
and support the transfer belt
130
in a predetermined tensioned state. In particular, reference numeral
132
denotes a driver roller that rotates the transfer belt
130
, reference numeral
134
denotes a backup roller that supports the transfer belt
130
against a transfer-to-paper roller
136
while the developed color image is transferred to a printing paper
90
and to which a voltage required for color image transfer is applied. Reference numerals
138
,
140
,
142
, and
144
denote first through fourth transfer rollers that contact the respective first through fourth photoreceptors
100
,
102
,
104
, and
106
, with the transfer belt
130
therebetween. The transfer rollers
138
,
140
,
142
and
144
transfer the developed images from the respective first through fourth photoreceptors
100
,
102
,
104
, and
106
to the transfer belt
130
. Since the developed images on the first through fourth photoreceptors
100
,
102
,
104
, and
106
are charged, the first through fourth transfer rollers
138
,
140
,
142
, and
144
may be charged to have a polarity opposite to a polarity of the first through fourth photoreceptors
100
,
102
,
104
, and
106
, respectively.
Although not illustrated in
FIG. 1
, the first through fourth transfer rollers
138
,
140
,
142
, and
144
are connected to separate power sources. Once a color image is transferred to the transfer belt
130
, subsequently the color image is transferred to the printing paper
90
. A voltage having a polarity opposite to the polarity of the voltage that is applied to the first through fourth transfer rollers
138
,
140
,
142
, and
144
must be applied to the backup roller
134
. Although not illustrated in
FIG. 1
, the backup roller
134
is also connected to a power source.
Reference numerals
120
,
122
,
124
, and
126
denote first through fourth developers, respectively, which constitute a single developer unit to develop the electrostatic latent images. The first through fourth developers
120
,
122
124
, and
126
supply ink of cyan, magenta, yellow, and black to the first through fourth photoreceptors
100
,
102
,
104
, and
106
, respectively, in order to develop the electrostatic latent images on the respective first through fourth photoreceptors
100
,
102
,
104
, and
106
. The first through fourth developers
120
,
122
,
124
, and
126
have the same internal structure. The ink of different colors is supplied to the first through fourth developers
120
,
122
,
124
, and
126
by respective first through fourth developing rollers
120
a
,
122
a
,
124
a
, and
126
a
, which are attached to the respective first through fourth developers
120
,
122
,
124
, and
126
.
Referring to
FIG. 2
, the first developer
120
includes a developer bath
120
c
filled with ink
120
b
to a predetermined height, the first developing roller
120
a
, which is partially immersed in the ink
120
b
and contacts the first photoreceptor
100
, and a cleaning roller
120
d
, which is immersed in the ink
120
b
and removes the unnecessary residual ink from the surface of the first developing roller
120
a
. The first developer
120
further includes an ink depositing roller
120
e
, which is immersed in the ink
120
b
and electrically deposits the ink
120
b
onto the surface of the first developing roller
120
a
from which the unnecessary residual ink has been removed, and a metering blade
120
f
, which is separated by a predetermined distance above the ink
120
b
and appropriately controls the thickness and concentration of the ink layer deposited on the first developing roller
120
a
by the ink depositing roller
120
e
. The ink depositing roller
120
e
is connected to a power source S to be able to electrically deposit the ink
120
b
on the first developing roller
120
a
. As a predetermined voltage is applied to the ink depositing roller
120
e
from the power source S, the ink
120
b
is electrically charged to be deposited onto the first developing roller
120
a.
As described above, since the developer unit of the conventional wet-type color image forming apparatus includes the metering blade installed around the developing roller, a high-concentration ink of about 3-18% or a constant amount of ink can be supplied to the transfer roller regardless of changes in the concentration of the ink. This is done so that images can be uniformly developed.
However, when toner particles are back-plated onto the surface of the developing roller, uniform development cannot be achieved. In other words, when toner particles are stuck in the space between the metering blade and the developing roller, when toner particles that have lost magneticity form clusters, when impurities are generated, or when the metering blade has a defect at its edge, the ink may be applied partially to the developing roller or in a low concentration. The non-uniform ink layer on the developing roller is transferred to the photoreceptor. As a result, a uniform, perfect color image, as shown in
FIG. 3
, cannot be achieved. Instead, the final color image may have a stripe pattern P, as shown in FIG.
4
.
SUMMARY OF THE INVENTION
Accordingly, it is an aspect of the present invention to provide a developer unit for a wet-type color image forming apparatus, capable of preventing image quality degradation due to toner impurities adhered to a developing roller or due to a defect in a metering roller.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and/or other aspects of the present invention may be achieved by providing a developer unit for a wet-type color image forming apparatus to develop an electrostatic latent image formed on a photoreceptor, including a developer bath filled with a liquid developing agent; a developing roller to develop the electrostatic latent image to correspond to an original image by supplying the liquid developing agent while being partially immersed in the liquid developing agent; a cleaning roller to clean a surface of the developing roller; a depositing roller to deposit the liquid developing agent onto the cleaned surface of the developing roller; a metering roller to adjust a
Kim Jong-woo
Park Woo-yong
Rutledge D.
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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